Architecture &AMP; Engineering

Best in State: Gold award Owner/client needs

Parsons Brinckerhoff designed a $6.9 million bridge span for Interstate 5 over the Skagit River that could be built in 90 days.

Parsons Brinckerhoff

Project: Interstate 5 Skagit River Bridge replacement

Client: Washington State Department of Transportation

Built in 1955, the Skagit River Bridge crosses the river between Mount Vernon and Burlington in northern Washington state. The bridge is a part of a heavily traveled section of Interstate 5, the primary transportation artery between Seattle and Vancouver, B.C., and an essential corridor for regional and international commerce.

On May 23, 2013, an over-height truck clipped a portion of the bridge’s steel truss, causing a 160-foot-long bridge span to collapse into the river.

On June 19, Max J. Kuney Co., with Parsons Brinckerhoff as designer, was selected by the Washington State Department of Transportation and given notice to proceed to construct the $6.87 million permanent bridge span replacement.

Parsons Brinckerhoff utilized its structural engineering familiarity with emergency bridge replacements in its work on the design-build team. The team prepared a design-and-construction scheme that met WSDOT’s maximum dead load requirements, minimized impacts to I-5 traffic, was constructible within the 90-day schedule, and resulted in the best value to WSDOT.

The team’s work successfully resulted in three significant achievements for WSDOT: the first emergency design-build contract using federal funds, the first decked bulb tee girder bridge design on an interstate highway in Washington, and the first use of lightweight aggregate by WSDOT for a concrete girder bridge of this type.

The new bridge span opened on Sept. 15, just 115 days after the initial accident and 88 days after the design-build team’s notice to proceed.